\documentclass{standalone}
\usepackage{tikz}
\usepackage{ctex,siunitx}
\setCJKmainfont{Noto Serif CJK SC}
\usepackage{tkz-euclide}
\usepackage{amsmath}
\usetikzlibrary{patterns, calc}
\usetikzlibrary {decorations.pathmorphing, decorations.pathreplacing, decorations.shapes,}
\begin{document}
\small
\begin{tikzpicture}[>=latex,scale=1.0]
  % \useasboundingbox(-0.6,-1.2)rectangle(3,1.2);
  \fill(0,1)to[bend left](0,-1)arc(-90:90:1);
  \draw[brown](0,-1)--(0,-0.2);
  \fill[ball color=brown!80!red](0,-0.2)circle(2pt);
  \fill[cyan!20,opacity=0.5,draw=black](0,0)circle(1);
  \draw[thin](0,-0.2)--++(135:1.5)node[left]{阳极};
  \draw[thin](45:1)--++(45:0.5)node[right]{阴极};
  \draw[thin](102:0.85)--++(90:0.3)node[above]{玻璃泡};
  \fill[ball color=gray](0.2,-1.38)circle(3pt);
  \fill[ball color=gray](-0.2,-1.38)circle(3pt);
  \fill[left color=gray,right color=gray,middle color=white](240:1)rectangle(0.5,-1.4);
\end{tikzpicture}
\end{document}